feat(Filters): Added Calendar Highlights section (fixes #924)

[HanzCEO]

Default	Present*	Verbose

* The current display on developers.events

[scraly]

Hi,
For the #924 issue, I imagined that in the calendar we want to have the event for:

• the start date
• in between
• and the end date

So I think adding options in the filter is not necessary, it should not become a "spaghetti dish" :).

Is it possible to fix the outcome without adding filter options but by displaying in the calendar the events for their start date, between the dates and their end date?

Thanks :)

[HanzCEO]

I will close this PR and work reconsider it whenever I have the time. Meanwhile, someone else might be able to salvage this. It is unfortunate that I am being held with many responsibilities right now.